Sketchpad: the first OO system

In his ACM Turing Award lecture at OOPSLA 2004, Alan Kay came up with this memorable quote about Sketchpad:

I went to ask Ivan How could you possibly in one year, in machine code, on this big but rather slow machine with no graphics display on it, have done the first graphics system, the first object-oriented software system, and the first dynamic problem-solving system?. And Ivan looked at me and said Well, I didn't know it was hard.